The present invention relates generally to monitoring of fluid flow and more specifically to an improved monitoring system for the delivery of petroleum products.
With petroleum becoming very expensive and even more so in the future, accurate measurement of the amount of petroleum products delivered to customers is increasingly important. Delivery trucks generally deliver gasoline to filling stations and fuel oil to residential or commercial accounts. The emphasis of prior art delivery devices is to provide a monitor at the truck in combination with the delivery ticket. A typical example is U.S. Pat. No. 3,366,967 to Sherman et al. This system provides an in-line flow monitor which actuates a time of day recorder at the beginning and end of fuel delivery as well as a lock for maintaining the ticket within the recording device for the printing of gallonage at the beginning and end of delivery. Although providing a certain degree of security for the oil companies and the customer, the delivery person had access to the delivery information and could alter it by other means. Thus there exists a need for a delivery monitor which is strictly under the control of the ultimate customer.
In order to provide a delivery monoitor which is economical enough and small enough to be owned and controlled by the ultimate customers, prior art flow rate meters are not applicable. They generally include rather bulky flow sensing devices and expensive circuitry. Similarly the accuracy of its measurement varies depending upon the configuration of the storage tank of the customer, temperature variations, pressure variations, as well as other factors. Similarly delivery of petroleum products offers a volatile environment which requires special safeguards.
Another ploy of bilking the customer is to flow water through the meter to run up the total. Thus there is a need for a flow delivery monitor which can determine when non-petroleum products are being delivered to the storage tank of the customer.